Maximal Value

There is an integer sequence A of length N whose values are unknown.

Given is an integer sequence B of length N-1 which is known to satisfy the following:

B_i \geq \max(A_i, A_{i+1})

Find the maximum possible sum of the elements of A.

Constraints

• All values in input are integers.
• 2 \leq N \leq 100
• 0 \leq B_i \leq 10^5

Input

Input is given from Standard Input in the following format:

N B_1 B_2 ... B_{N-1}

Output

Print the maximum possible sum of the elements of A.

Examples

Input

3 2 5

Output

9

Input

2 3

Output

6

Input

6 0 153 10 10 23

Output

53

inputFormat

input are integers.

• 2 \leq N \leq 100
• 0 \leq B_i \leq 10^5

Input

Input is given from Standard Input in the following format:

N B_1 B_2 ... B_{N-1}

outputFormat

Output

Print the maximum possible sum of the elements of A.

Examples

Input

3 2 5

Output

9

Input

2 3

Output

6

Input

6 0 153 10 10 23

Output

53

样例

2
3

6